Methods of Forming Semiconductor Devices

ABSTRACT

Provided are a semiconductor device and a method of forming the same. The method may include forming a metal oxide layer on a substrate and forming a sacrificial oxide layer on the metal oxide layer. An annealing process is performed on the substrate. A formation-free energy of the sacrificial oxide layer is greater than a formation-free energy of the metal oxide layer at a process temperature of the annealing process.

REFERENCE TO PRIORITY APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/581,223, filed Oct. 19, 2009, which claims the benefit of KoreanPatent Application No. 10-2008-0103197, filed Oct. 21, 2008, thecontents of which are hereby incorporated herein by reference.

FIELD OF THE INVENTION

The embodiments disclosed herein relate to semiconductor devices andmethods of forming the same and, more particularly, to semiconductordevices including dielectric layers and methods of forming the same.

BACKGROUND

As a semiconductor industry is highly developed, a high integration of asemiconductor device is deepened. That is, a minimum line width andthickness of layers (e.g., a conductive layer and/or a dielectric layer)of a semiconductor device becomes increasingly minute. A lot of problemsmay occur due to a miniature of a semiconductor device. For example,degradation of an operation speed, an increase of power consumptionand/or degradation of reliability may occur. In contrast, user'srequirements for an improvement of various characteristics (e.g., highspeed, low power consumption and/or high reliability) of a semiconductordevice are increased more and more. A lot of studies of a semiconductordevice are being performed to meet the miniature and user'srequirements.

SUMMARY

Exemplary embodiments provide a method of forming a semiconductordevice. The method may include forming a metal oxide layer on asubstrate; forming a sacrificial oxide layer on the metal oxide layer;and performing an annealing process on the substrate including thesacrificial oxide layer. A formation-free energy of the sacrificialoxide layer is greater than a formation-free energy of the metal oxidelayer at a process temperature of the annealing process.

Exemplary embodiments provide a semiconductor device. The semiconductordevice may include a substrate; and a metal oxide layer disposed on thesubstrate, the metal oxide layer including a specific element and atleast one metal element, wherein reactivity between the specific elementand oxygen is smaller than reactivity between the metal element andoxygen.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying figures are included to provide a further understandingof the present invention, and are incorporated in and constitute a partof this specification. The drawings illustrate exemplary embodiments ofthe present invention and, together with the description, serve toexplain principles of the present invention. In the figures:

FIGS. 1 through 3 are cross-sectional views illustrating a method offorming a semiconductor device according to an embodiment of the presentinvention.

FIG. 4 is a cross-sectional view of a semiconductor device according toan embodiment of the present invention.

FIG. 5 is a graph illustrating a specific element concentration in ametal oxide layer of a semiconductor device according to an embodimentof the present invention, the graph being taken along the line I-I′ ofFIG. 4.

FIG. 6 is an energy band diagram of a semiconductor device according toan embodiment of the present invention, the energy band diagram beingtaken along the line I-I′ of FIG. 4.

FIGS. 7 through 10 are cross-sectional views illustrating a method offorming a semiconductor device according to another embodiment of thepresent invention.

FIG. 11 is a cross-sectional view of a semiconductor device according toanother embodiment of the present invention.

FIG. 12 is a cross-sectional view of a semiconductor device according tostill another embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. In thedrawings, the size and relative sizes of layers and regions may beexaggerated for clarity. Like numbers refer to like elements throughout.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. As used herein, the term “and/or” includesany and all combinations of one or more of the associated listed itemsand may be abbreviated as “/”.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first region/layer could be termeda second region/layer, and, similarly, a second region/layer could betermed a first region/layer without departing from the teachings of thedisclosure.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

Embodiments of the present invention may be described with reference tocross-sectional illustrations, which are schematic illustrations ofidealized embodiments of the present invention. As such, variations fromthe shapes of the illustrations, as a result, for example, ofmanufacturing techniques and/or tolerances, are to be expected. Thus,embodiments of the present invention should not be construed as limitedto the particular shapes of regions illustrated herein, but are toinclude deviations in shapes that result from, e.g., manufacturing. Forexample, a region illustrated as a rectangle may have rounded or curvedfeatures. Thus, the regions illustrated in the figures are schematic innature and are not intended to limit the scope of the present invention.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and/orthe present application, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

In the drawings, the thickness of layers and regions are exaggerated forclarity. It will also be understood that when an element such as alayer, region or substrate is referred to as being “on” or “onto”another element, it may lie directly on the other element or interveningelements or layers may also be present. Like reference numerals refer tolike elements throughout the specification.

Spatially relatively terms, such as “beneath,” “below,” “above,”“upper,” “top,” “bottom” and the like, may be used to describe anelement and/or feature's relationship to another element(s) and/orfeature(s) as, for example, illustrated in the figures. It will beunderstood that the spatially relative terms are intended to encompassdifferent orientations of the device in use and/or operation in additionto the orientation depicted in the figures. For example, when the devicein the figures is turned over, elements described as below and/orbeneath other elements or features would then be oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly. As used herein, “height” refers toa direction that is generally orthogonal to the faces of a substrate.

First Embodiment

FIGS. 1 through 3 are cross-sectional views illustrating a method offorming a semiconductor device according to an embodiment of the presentinvention.

Referring to FIG, 1, an interface layer 102 may be formed on a substrate100. A metal oxide layer 108 may be formed on the interface layer 102.The substrate 100 may include a semiconductor layer. The semiconductorlayer may be a portion (e.g., an upper portion) of a semiconductorsubstrate. Unlike this, the semiconductor layer may be disposed on aninsulating layer on a semiconductor substrate. The semiconductor layermay include silicon, germanium or silicon-germanium. However, thepresent invention is not limited to here. In an embodiment, thesubstrate 100 may include a conductor used as an electrode disposed on asemiconductor substrate.

The interface layer 102 may perform a function of inhibiting a reactionbetween the metal oxide layer 108 and the substrate 100. The interfacelayer 102 may include an oxide layer, an oxynitride layer and/or anitride layer. In the case that the semiconductor layer of the substrate100 includes silicon, the interface layer 102 may include a siliconoxide layer by a thermal oxidation process, a silicon oxynitride layerby a thermal oxidation process and a nitration process, and/or a siliconnitride layer by a nitration process. Since the interface layer 102 isformed by a thermal oxidation process and/or a thermal oxidationprocess, the interface layer 102 may have a very dense structure. Theinterface layer 102 may be omitted.

The metal oxide layer 108 may have a dielectric constant higher thanthat of a silicon oxide layer. The metal oxide layer 108 may besingle-layered or multi-layered. For example, the metal oxide layer 108may include a first metal oxide layer 104 and a second metal oxide layer106 that are sequentially stacked. That is, the first metal oxide layer104 may be formed on the interface layer 102 and the second metal oxidelayer 106 may be formed on the first metal oxide layer 104. As describedabove, the first and second metal oxide layers 104 and 106 may have adielectric constant higher than that of a silicon oxide layer. The firstmetal oxide layer 104 may include a first metal element and oxygen andthe second metal oxide layer 106 may include a second metal element andoxygen. The first and second metal elements may be different from eachother. The metal oxide layer 108 may include at least one selected fromthe group consisting of a hafnium oxide layer (HfO₂), a lanthanum oxidelayer (La₂O₃), a zirconium oxide layer (ZrO₂), a dysprosium oxide layer(Dy₂O₃), an yttrium oxide layer (Y₂O₃), an aluminum oxide layer (Al₂O₃),a scandium oxide layer (Sc₂O₃) and an erbium oxide layer (Er₂O₃). Thefirst and second metal oxides 104 and 106 may be formed of differentmetal oxide from each other.

A sacrificial oxide layer 110 is formed on the metal oxide layer 108.The sacrificial oxide layer 110 may include a specific element andoxygen. The sacrificial oxide layer 110 may be formed by using a processsuch as a chemical vapor deposition(CVD) process and/or an atomic layerdeposition(ALD) process. The sacrificial oxide layer 110 may be formedunder a process temperature lower than a minimum temperature requiredwhen elements in the metal oxide layer 108 are activated. Accordingly,when the sacrificial oxide layer 110 is formed, elements in the metaloxide layer 108 may not be activated.

Referring to FIG. 2, an annealing process is performed on the substrate100 including the sacrificial oxide layer 110 and the metal oxide layer108. A process temperature of the annealing process may be equal to orgreater than a minimum temperature required when elements (e.g., thefirst metal element, the second metal element, the specific element andoxygen) in the sacrificial oxide layer 110 and the metal oxide layer 108are activated. The process temperature of the annealing process may befrom about 600° C. to about 1100° C. A process gas of the annealingprocess may include an inert gas (e.g., nitrogen gas (N₂) or argon gas).

Each of the metal oxide layer 108 and the sacrificial oxide layer 110has Gibbs free energy of formation. Hereinafter, the Gibbs free energyof formation is referred as formation-free energy. The formation-freeenergy is a thermodynamic quantity representing a degree of spontaneityof a reaction. At the process temperature of the annealing process, theformation-free energy of the sacrificial oxide layer 110 may be greaterthan the formation-free energy of the metal oxide layer 108.Accordingly, when the annealing process is performed, reactivity betweenoxygen and the specific element in the sacrificial oxide layer 110 issmaller than reactivity between oxygen and metal elements in the metaloxide layer 108. The formation-free energy of the sacrificial oxidelayer 110 and the formation-free energy of the metal oxide layer 108 maybe a negative number. That is, the sacrificial oxide layer 110 and themetal oxide layer 108 may be material generated from a spontaneousreaction.

Since the formation-free energy of the sacrificial oxide layer 110 isgreater than the formation-free energy of the metal oxide layer 108 atthe process temperature of the annealing process, oxygen in thesacrificial oxide layer 110 may be supplied to the metal oxide layer 108during the annealing process. More specifically, the specific elementand oxygen in the sacrificial oxide layer 110 and the metal elements andoxygen in the metal oxide layer 108 are activated during the annealingprocess. At this time, oxygen in the sacrificial oxide layer 110 may becombined with the metal elements having a strong reactivity in the metaloxide layer 108 during the annealing process. That is, oxygen in thesacrificial oxide layer 110 may be supplied to the metal oxide layer10.8. The supplied oxygen may be combined with vacancies in the annealedmetal oxide layer 108 a. As a result, vacancies in the annealed metaloxide layer 108 a can be minimized. When the metal oxide layer 108 is asingle layer, bulk vacancies in the annealed metal oxide layer 108 a canbe minimized by the sacrificial oxide layer 110 and the annealingprocess. The annealed sacrificial oxide layer 110′ may be in anoxygen-lacked state.

Next, the case that the metal oxide layer 108 includes the first metaloxide layer 104 and the second metal oxide layer 106 will be describedin detail. The formation-free energy of the sacrificial oxide layer 110may be greater than a formation-free energy of the first metal oxidelayer 104 and a formation-free energy of the second metal oxide layer106 at the process temperature of the annealing process. The processtemperature of the annealing process may be equal to or greater than aminimum temperature required when the first metal element and oxygen ofthe first metal oxide layer 104, the second metal element and oxygen ofthe second metal oxide layer 106 and the specific element and oxygen ofthe sacrificial oxide layer 110 are activated. The formation-free energyof the first metal oxide layer 104 and the formation-free energy of thesecond metal oxide layer 106 may be different from each other. The firstmetal oxide layer 104 and the second metal oxide layer 106 may becombined with each other by the annealing process to generate acombination layer 107. That is, the annealed metal oxide layer 108 a mayinclude the combination layer 107. The combination layer 107 may includethe first metal element, the second metal element and oxygen. Since theformation-free energy of the first metal oxide layer 104 and theformation-free energy of the second metal oxide layer 106 are differentfrom each other, not only bulk vacancies but also vacancies generated bya combination may exist in the combination layer 107. At this time,oxygen in the sacrificial oxide layer 110 is supplied to the combinationlayer 107 to minimize vacancies in the combination layer 107.

For example, the sacrificial oxide layer 110 may include at least oneselected from the group consisting of a silicon oxide layer (SiO₂), amagnesium oxide layer (MgO), a calcium oxide layer (CaO), a berylliumoxide layer (BeO), a nickel oxide layer (NiO), a lithium oxide layer(LiO) and a germanium oxide layer (GeO₂ or GeO).

For example, the first metal oxide layer 104 may be formed of a hafniumoxide layer (HfO₂) and the second metal oxide layer 106 may be formed ofan aluminum oxide layer (Al₂O₃). In this case, the sacrificial oxidelayer 110 may be formed of a silicon oxide layer (SiO₂). Aformation-free energy of a hafnium oxide layer (HfO₂) is about −1217KJ/mol at about 950° C., a formation-free energy of an aluminum oxidelayer (Al₂O₃) is about −1738 KJ/mol at about 950° C. and aformation-free energy of a silicon oxide layer (SiO₂) is −962 KJ/mol atabout 950° C. That is, a formation-free energy of the sacrificial oxidelayer 110 formed of a silicon oxide layer (SiO₂) is greater thanformation-free energies of the first and second metal oxide layers 104and 106 respectively formed of a hafnium oxide layer (HfO₂) and analuminum oxide layer (Al₂O₃).

As depicted in FIG. 2, a portion of the second metal oxide layer 106 maybe combined with the first metal oxide layer 104 by the annealingprocess. In this case, a remaining layer 106′ of the second metal oxidelayer may be disposed on the combination layer 107. The annealed metaloxide layer 108 a may include the combination layer 107 and theremaining layer 106′ of the second metal oxide layer. The remaininglayer 106′ may include the second metal element and oxygen. Oxygen inthe sacrificial oxide layer 110 is also supplied to the remaining layer106′. Accordingly, even when the formation-free energy of the secondmetal oxide layer 106 is greater than the formation-free energy of thefirst metal oxide layer 104, vacancies of the remaining layer 106′ maybe minimized by oxygen in the sacrificial oxide layer 110. Unlike this,an entire portion of the second metal oxide layer 106 may be combinedwith the first metal oxide layer 104. In this case, the remaining layer106′ is not formed and the annealed metal oxide layer 108 a may includethe combination layer 107.

Referring to FIG. 3, the annealed sacrificial oxide layer 110′ isremoved. According to an embodiment, the annealed sacrificial oxidelayer 110′ and the remaining layer 106′ may be removed after performingthe annealing process, such that the annealed metal oxide layer 108 amay include the combination layer 107. According to an embodiment, afterremoving the annealed sacrificial oxide layer 110′, the annealed metaloxide layer 108 a may include the specific element of the sacrificialoxide layer 110.

After removing the annealed sacrificial oxide layer 110′, an electrode115 of FIG. 4 may be formed on the substrate 100. The electrode 115 maybe formed on the annealed metal oxide layer 108 a. The electrode 115 maybe directly formed on the combination layer 107 or on the remaininglayer 106′. The combination layer 107 may shift a Fermi-level of theelectrode 115 of FIG. 4. Thus, an effective work function of theelectrode 115 may be changed. Further details of the effective workfunction of the electrode 115 will be described later referring to FIG.4. The annealed metal oxide layer 108 a may be used as a dielectriclayer of various uses. For example, the annealed metal oxide layer 108 amay be used as a gate dielectric layer of a transistor or a capacitordielectric layer of a capacitor.

According to the method of forming a semiconductor device describedabove, oxygen in the sacrificial oxide layer 110 is supplied to themetal oxide layer 108 during the annealing process. Accordingly,vacancies in the annealed metal oxide layer 108 a can be minimized. As aresult, an electrical characteristic of the annealed metal oxide layer108 a may be improved.

Vacancies in a dielectric layer may cause some problems. For example,the vacancies in the dielectric layer may trap charges. Thus, anelectric potential of the dielectric layer having the vacancies may bechanged to cause a deterioration of a characteristic of a semiconductordevice. Also, charges may penetrate the dielectric layer via thevacancies in the dielectric layer. Accordingly, a characteristic of aleakage current of the dielectric layer may be deteriorated. Inaddition, when the dielectric layer having the vacancies is used as agate dielectric layer, the vacancies may decrease a mobility of carriesin a channel. However, according to an embodiment of the presentinvention, vacancies in the annealed metal oxide layer 108 a areminimized by the sacrificial oxide layer 110 and the annealing process.Thus, a dielectric layer including the annealed metal oxide layer 108 ahaving a superior electrical characteristic can be embodied.

Oxygen in the sacrificial oxide layer 110 can be diffused into the metaloxide layer 108 by performing the annealing process after forming thesacrificial oxide layer 110. Thus, oxygen in the sacrificial oxide layer110 can be stably supplied to the metal oxide layer 108. As a result, aneffect that oxygen in the sacrificial oxide layer 110 applies to asubstrate under the metal oxide layer 108 can be minimized.

FIG. 4 is a cross-sectional view of a semiconductor device according toan embodiment of the present invention.

Referring to FIG. 4, a metal oxide layer 108 a is disposed on asubstrate 100. An interface layer 102 may be disposed between the metaloxide layer 108 a and the substrate 100. The interface layer 102 mayinclude oxide, nitride and/or oxynitride. The interface layer 102 may beomitted. An electrode 115 may be disposed on the metal oxide layer 108a. The electrode 115 may include at least one selected from the groupconsisting of a doped semiconductor, a conductive metal nitride (e.g.,titanium nitride or tantalum nitride), metal silicide (e.g., tungstensilicide or cobalt silicide) and metal (e.g., titanium, tantalum,copper, aluminum or noble metal).

The metal oxide layer 108 a may include oxygen and at least one metalelement. In addition, the metal oxide layer 108 a may include a specificelement. Reactivity between the specific element and oxygen may besmaller than reactivity between the metal element and oxygen. In otherwords, a reduction potential of the specific element may be smaller thana reduction potential of the metal element. According to an embodimentof the present invention, the metal oxide layer 108 a may include afirst metal element, a second metal element, oxygen and the specificelement. In this case, the reactivity between the specific element andoxygen may be smaller than reactivity between the first metal elementand oxygen and reactivity between the second metal element and oxygen.That is, a reduction potential of the specific element may be smallerthan a reduction potential of the first metal element and a reductionpotential of the second metal element. The first metal element may be ametal element included in the first metal oxide layer 104 of FIG. 1 andthe second metal element may be a metal element included in the secondmetal oxide layer 106 of FIG. 1.

The metal oxide layer 108 a may include a combination layer 107including the first metal element, the second metal element and oxygen,and a capping layer 106′ disposed on the combination layer 107. Thecapping layer 106′ may include the second metal element and oxygen. Thecapping layer 106′ may not include the first metal element. The cappinglayer 106′ may correspond to the remaining layer 106′ of FIG. 2. Unlikethis, the metal oxide layer 108 a may be composed of only thecombination layer 107 without the capping layer 106′.

A concentration of the specific element in the metal oxide layer 108 amay be different depending on a location of the metal oxide layer 108 a.

FIG. 5 is a graph illustrating a specific element concentration in ametal oxide layer of a semiconductor device according to an embodimentof the present invention, the graph being taken along the line I-I′ ofFIG. 4.

Referring to FIGS. 4 and 5, a y axis represents a concentration of thespecific element and an x axis represents a location in FIG. 5. Themetal oxide layer 108 a has first surface and second surface facing eachother. The first surface of the metal oxide layer 108 a is disposed tobe relatively away from the removed sacrificial oxide layer (110′ ofFIG. 2) compared with the second surface. The second surface of themetal oxide layer 108 a is disposed to be relatively close to theremoved sacrificial oxide layer (110′ of FIG. 2) compared with the firstsurface. For example, the first surface of the metal oxide layer 108 amay correspond to a lower surface of the metal oxide layer 108 a and thesecond surface of the metal oxide layer 108 a may correspond to an uppersurface of the metal oxide layer 108 a. In FIG. 5, the first surface ofthe metal oxide layer 108 a is adjacent to the interface layer 102 andthe second surface of the metal oxide layer 108 a is adjacent to theelectrode 115. When the metal oxide layer 108 a includes the combinationlayer 107 and the capping layer 106′, the second surface of the metaloxide layer 108 a may correspond to an upper surface of the cappinglayer 106′. When the metal oxide layer 108 a include only thecombination layer 107, the second surface of the metal oxide layer 108 amay correspond to an upper surface of the combination layer 107.

A line 120 of FIG. 5 represents a concentration of the specific element.As depicted in FIG. 5, a concentration of the specific element of aportion of the metal oxide layer 108 a adjacent to the first surface isdifferent from a concentration of the specific element of a portion ofthe metal oxide layer 108 a adjacent to the second surface. Theconcentration of the specific element of the portion of the metal oxidelayer 108 a adjacent to the second surface may be greater than theconcentration of the specific element of the portion of the metal oxidelayer 108 a adjacent to the first surface. The portion of the metaloxide layer 108 a adjacent to the second surface may have a significantconcentration of the specific element. As a location in the metal oxidelayer 108 a moves from the second surface toward the first surface, theconcentration of the specific element may be abruptly decreased.

the concentration of the specific element is very small compared with aconcentration of the metal element in the metal oxide layer 108 a. Forexample, a maximum value of a concentration of the specific element maybe 10⁻⁵% to several % of a concentration of the metal element in themetal oxide layer 108 a.

The metal oxide layer 108 a including the combination layer 107 mayshift a Fermi level of the electrode 115.

FIG. 6 is an energy band diagram of a semiconductor device according toan embodiment of the present invention, the energy band diagram beingtaken along the line I-I′ of FIG. 4. An energy band diagram of FIG. 6 isa simplified thing for convenience of an explanation.

Referring to FIGS. 4 and 6, the combination layer 107 includes firstsurface and second surface facing each other. A first interface may beformed by the first surface of the combination layer 107 and theinterface layer 102. When the interface layer 102 is omitted, the firstinterface may be formed by the first surface of the combination layer107 and the substrate 100. A second interface may be formed by thesecond surface of the combination layer 107 and the capping layer 106′.When the capping layer 106′ is omitted, the second interface may beformed by the second surface of the combination layer 107 and theelectrode 115.

The combination layer 107 may change an interface state of the firstinterface. Thus, a band offset between the combination layer 107 and theinterface layer 102 may be changed. The band offset may be defined by anenergy difference between conduction band edges of two layers that arein contact with each other. The band offset between the combinationlayer 107 and the interface layer 102 is an energy difference between aconduction band edge of the combination layer 107 and a conduction bandedge of the interface layer 102.

As the band offset between the combination layer 107 and the interfacelayer 102 is changed, a Fermi level of the electrode 115 may be shifted.In FIG. 6, a reference numeral 140 is a natural Fermi level of theelectrode 115 and a reference numeral 145 of FIG. 6 represents a shiftedFermi level of the electrode 115. A dotted line of the metal oxide layer108 a in FIG. 6 represents natural energy bands of the combination layer107 and the capping layer 106′.

The combination layer 107 changes an interface state of the secondinterface, thereby changing a band offset between the combination layer107 and the capping layer 106′ (or the electrode 115). In this case, aband offset variation at the second interface may be different from aband offset variation at the first interface. Band offset variations ofthe first and second interfaces may be a positive number or a negativenumber. When the band offset variation is a negative number, the shiftedband offset is decreased compared with the natural band offset. When theband offset variation is a positive number, the shifted band offset isincreased compared with the natural band offset. Accordingly, a Fermilevel of the electrode 115 may be shifted by a band offset variation dueto the combination layer 107. A portion of the combination layer 107adjacent to the first surface of the combination layer 107 and a portionof combination layer 107 adjacent to the second surface of thecombination layer 107 may have a different content ratio from eachother. In other words, a first metal element concentration and a secondmetal element concentration of the portion of the combination layer 107adjacent to the first surface may be different from a first metalelement concentration and a second metal element concentration of theportion of the combination layer 107 adjacent to the second surface,respectively.

The Fermi level of the electrode 115 may be increased by the combinationlayer 107. For example, when one of the first and second metal elementsin the combination layer 107 is aluminum, a Fermi level of the electrode115 may be increased. In this case, an aluminum concentration in theportion of the combination layer 107 adjacent to the first surface ofthe combination layer 107 may be greater than an aluminum concentrationin the portion of the combination layer 107 adjacent to the secondsurface of the combination layer 107. In this case, the other of thefirst and second metal elements in the combination layer 107 may behafnium.

A Fermi level of the electrode 115 may be decreased by the combinationlayer 107. For example, when one of the first and second metal elementsin the combination layer 107 is one of zirconium and rare-earth metal(e.g., lanthanum (La), dysprosium (Dy) or erbium (Er)), a Fermi level ofthe electrode 115 may be decreased. In this case, a zirconiumconcentration (or rare-earth metal concentration) in the portion of thecombination layer 107 adjacent to the first surface of the combination107 may be greater than a zirconium concentration (or rare-earth metalconcentration) in the portion of the combination layer 107 adjacent tothe second surface of the combination 107.

Second Embodiment

The present embodiment discloses a semiconductor device includingtransistors according to an embodiment of the present invention. Inparticular, the present embodiment discloses a semiconductor deviceincluding an NMOS transistor and a PMOS transistor. In the presentembodiment, elements identical to the first embodiment described aboveuse like reference numerals.

FIGS. 7 through 10 are cross-sectional views illustrating a method offorming a semiconductor device according to another embodiment of thepresent invention.

Referring to FIG. 7, an interface layer 102 may be formed on a substrate100 including a first region (a) and a second region (b). A metal oxidelayer 108 may be formed on the interface layer 102. Before forming theinterface layer 102, a device isolation pattern (not shown) may beformed in the substrate 100 to define a first active portion in thefirst region (a) and a second active portion in the second region (b).The first and second active portions may be a portion of the substrate100 surrounded by the device isolation pattern. One of the first region(a) and the second region (b) is a region where a PMOS transistor isformed and the other is a region where a NMOS transistor is formed.

The metal oxide layer 108 may be single-layered or multi-layered. Themetal oxide layer 108 may include a first metal oxide layer 104 and asecond metal oxide layer 106 that are sequentially stacked. Asacrificial oxide layer 110 is formed on the metal oxide layer 108. Thefirst metal oxide layer 104, the second metal oxide layer 106 and thesacrificial oxide layer 110 may be identical to the first embodimentdescribed above. The sacrificial oxide layer 110 may be formed at atemperature lower than a minimum temperature required when a first metalelement, a second metal element and oxygen in the first and second metaloxide layer 104 and 106 are activated.

Referring to FIG.8, the sacrificial oxide layer 110 and the second metaloxide layer in the second region (b) may be removed. At this time, thesacrificial oxide layer 110 and the second metal oxide layer in thefirst region (a) remain. A mask pattern (not shown) covering thesacrificial oxide layer 110 in the first region (a) may be formed andthe sacrificial oxide layer 110 and the second metal oxide layer inn thesecond region (b) may be removed using the mask pattern as an etchingmask. Subsequently, the mask pattern may be removed.

Referring to FIG. 9, an annealing process is performed on the substrate100. The annealing process may be identical to the annealing process ofthe first embodiment described above. Accordingly, when the annealingprocess is performed, the first metal oxide layer 104 and the secondmetal oxide layer 106 in the first region (a) are combined with eachother to form a combination layer 107 and oxygen in the sacrificialoxide layer 110 is supplied to the combination layer 107. As depicted inFIG. 9, a portion of the second metal oxide layer 106 is combined withthe first metal oxide layer 104 and the other portion 106′ of the secondmetal oxide layer 106 may remain. Oxygen in the sacrificial oxide layer110 may be supplied to a remaining layer 106′. Thus, vacancies in anannealed metal oxide layer 108 a are minimized. The second metal oxidelayer 106 does not exist in the second region (b). Therefore, when theannealing process is performed, the first metal oxide layer 104 in thesecond region (b) may not be combined.

Referring to FIG. 10, an annealed sacrificial oxide layer 110′ isremoved. As described referring to FIG. 4, after removing the annealedsacrificial oxide layer 110′, a portion of the specific element in thesacrificial oxide layer 110 may remain in the annealed metal oxide layer108 a, The remaining layer 106′ may be removed according to acharacteristic required by a semiconductor device. Unlike this, theremaining layer 106′ may remain.

A gate conductive layer 115 is formed on the combination layer 107 inthe first region (a) and the first metal oxide layer 104 in the secondregion (b). The gate conductive layer 115 may include at least oneselected from the group consisting of a doped semiconductor, conductivemetal nitride (e.g., titanium nitride or tantalum nitride), metalsilicide (e.g., tungsten silicide or cobalt silicide) and metal (e.g.,titanium, tantalum, copper, aluminum or noble metal).

The gate conductive layer 115 is patterned to form a first gateelectrode 115 a and a second gate electrode 115 b of FIG. 11. The firstgate electrode 115 a is formed on the combination layer 107 of the firstregion (a) and the second gate electrode 115 b is formed on the firstmetal oxide layer 104 of the second region (b). A first source/drain 117a and a second source/drain 117 b of FIG. 11 are formed. The first andsecond sources/drains 117 a and 117 b may be simultaneously orsequentially formed. The first and second sources/drains 117 a and 117 bmay be doped with dopants of opposite types. That is, one of the firstand second sources/drains 117 a and 117 b may be doped with n typedopants and the other may be doped with p type dopants. The first gateelectrode 115 a, the combination layer 107 and the first source/drain117 a are included in a first transistor and the second gate electrode115 b, the first metal oxide layer 104 and the second source/drain 117 bare included in a second transistor.

According to the method of forming a semiconductor device describedabove, oxygen in the sacrificial oxide layer 110 of the first region (a)is supplied to the metal oxide layer 108. Thus, quantity of vacancies inthe annealed metal oxide layer 108 a of the first region (a) areminimized and the first transistor has a superior electricalcharacteristic.

Also, a Fermi level of the first gate electrode 115 a may be shifted bythe combination layer 107. Accordingly, even though the first and secondgate electrodes 115 a and 115 b may be formed of the same material, aFermi level of the first gate electrode 115 a may be different from aFermi level of the second gate electrode 115 b. As a result, a CMOSdevice having a optimized NMOS transistor and a optimized PMOStransistor can be embodied.

For example, when the first gate electrode 115 a is adjacent to a Fermilevel of n type silicon and the second gate electrode 115 b is adjacentto a Fermi level of p type silicon, the first transistor may be a NMOStransistor and the second transistor may be a PMOS transistor. Unlikethis, when the first gate electrode 115 a is adjacent to a Fermi levelof p type silicon and the second gate electrode 115 b is adjacent to aFermi level of n type silicon, the first transistor may be a PMOStransistor and the second transistor may be a NMOS transistor.

FIG. 11 is a cross-sectional view of a semiconductor device according toanother embodiment of the present invention.

Referring to FIG. 11, a device isolation pattern (not shown) is disposedin a substrate 100 including a first region (a) and a second region (b)to define a first active portion in the first region (a) and a secondactive portion in the second region (b). The first and second activeportions may be a portion of the substrate 100 surrounded by the deviceisolation pattern. A first gate electrode 115 a crosses over the firstactive portion and a second gate electrode 115 b crosses the secondactive portion. A combination layer 107 including a first metal element,a second metal element and oxygen is disposed between the first gateelectrode 115 a and the first active portion. A capping layer (106′ ofFIG. 9) including a second metal element and oxygen may be disposedbetween the combination layer 107 and the first gate electrode 115 a. Afirst metal oxide layer 104 including the first metal element and oxygenis disposed between the second gate electrode 115 b and the secondactive portion. An interface layer 102 may be disposed between thecombination layer 107 and the first active portion and between the metaloxide layer 104 and the second active portion. A first source/drain 117a may be disposed in the first active portion of both sides of the firstgate electrode 115 a and a second source/drain 117 b may be disposed inthe second active portion of both sides of the second gate electrode 115b.

The combination layer 107 or the combination layer 107/capping layerincludes a specific element. Reactivity between the specific element andoxygen may be smaller than reactivity between the first metal elementand oxygen and between the second metal element and oxygen. Aconcentration of the specific element in the combination layer 107 maybe identical to the concentration described referring to FIG. 5. Thefirst metal oxide layer 140 between the second gate electrode 115 b andthe second active portion may not include the specific element.

The first and second gate electrodes 115 a and 115 b may be formed ofthe same material. A Fermi level of the first gate electrode 115 a maybe shifted by the combination layer 107. Accordingly, an effective workfunction of the first gate electrode 115 a may become different from aneffective work function of the second gate electrode 115 b. One of thefirst and second gate electrodes 115 a and 115 b may be used as a gateof a NMOS transistor and the other may be used as a gate of a PMOStransistor. Consequently, a NMOS transistor and a PMOS transistor havinga superior characteristic can be embodied.

Third Embodiment

The present embodiment discloses a semiconductor device including acapacitor according to an embodiment of the present invention. In thepresent embodiment, elements identical to the first and secondembodiments described above use like reference numerals.

FIG. 12 is a cross-sectional view of a semiconductor device according tostill another embodiment of the present invention.

Referring to FIG. 12, a metal oxide layer 108 a is disposed on asubstrate 100′, The substrate 100′ may include a first electrode 95. Inaddition, the substrate 100′ may further include a support substrate 90under the first electrode 95. That is, the first electrode 95 may bedisposed on the support substrate 90. The support substrate 90 mayinclude a semiconductor substrate, or a semiconductor substrate and aninsulating layer that are sequentially stacked. The first electrode 95may include at least one selected from the group consisting of a dopedsemiconductor, conductive metal nitride (e.g., titanium nitride ortantalum nitride), metal silicide (e.g., tungsten silicide or cobaltsilicide) and metal (e.g., titanium, tantalum, copper, aluminum or noblemetal).

The metal oxide layer 108 a may be disposed on the first electrode 95.An interface layer 102 may be disposed between the metal oxide layer 108a and the first electrode 95. A second electrode 115 may be disposed onthe metal oxide layer 108 a. The metal oxide layer 108 a, or theinterface layer 102/the metal oxide layer 108 a may be used as adielectric layer of a capacitor. The first electrode 95 and the secondelectrode 115 correspond to both electrodes of a capacitor.

The metal oxide layer 108 a may include a first metal element, a secondmetal element and oxygen. In addition, the metal oxide layer 108 a mayfurther include a specific element. Reactivity between the specificelement and oxygen may be smaller than reactivity between the firstelement and oxygen and reactivity between the second element and oxygen.The metal oxide layer 108 a may include a combination layer 107 and acapping layer 106′. The combination layer 107 may include the firstmetal element, the second metal element and oxygen and the capping layer106′may include the second metal element and oxygen. The capping layer106′may be omitted. A concentration of the specific element in the metaloxide layer 108 a may be equal to the concentration described referringto FIG. 5 in the first embodiment described above. As described in thefirst and second embodiments, the combination layer 107 may shift a workfunction of the second electrode 115. Thus, a leakage current of acapacitor can be all the more minimized by controlling a difference of awork function between the first and second electrodes 95 and 115.

A capacitor including the first electrode 95, the second electrode 115and the metal oxide layer 108 a may be embodied to have various shapessuch as a flat shape, a cylinder shape or a stack shape.

The foregoing is illustrative of the present invention and is not to beconstrued as limiting thereof. Although a few embodiments of the presentinvention have been described, those skilled in the art will readilyappreciate that many modifications are possible in the embodimentswithout materially departing from the novel teachings and advantages ofthe present invention. Accordingly, all such modifications are intendedto be included within the scope of the present invention as defined inthe claims. Therefore, it is to be understood that the foregoing isillustrative of the present invention and is not to be construed aslimited to the specific embodiments disclosed, and that modifications tothe disclosed embodiments, as well as other embodiments, are intended tobe included within the scope of the appended claims. The presentinvention is defined by the following claims, with equivalents of theclaims to be included therein.

1. A method of forming a semiconductor device, comprising: forming ametal oxide layer on a substrate; forming a sacrificial oxide layer onthe metal oxide layer; and performing an annealing process on thesubstrate including the sacrificial oxide layer, wherein aformation-free energy of the sacrificial oxide layer is greater than aformation-free energy of the metal oxide layer at a process temperatureof the annealing process; wherein forming the metal oxide layercomprises: forming a first metal oxide layer on the substrate; andforming a second metal oxide layer on the first metal oxide layer;wherein the formation-free energy of the sacrificial oxide layer isgreater than a formation-free energy of the first metal oxide layer anda formation-free energy of the second metal oxide layer at the processtemperature of the annealing process; and wherein the first and secondmetal oxide layers are combined with each other by the annealing processto form a combination layer.